This invention relates to a voltage to frequency converter which generates an output pulse string whose output frequency is proportional to the square of an applied voltage signal.
Voltage to frequency converters are well known. One such voltage to frequency converter is described in U.S. Pat. No. 4,303,985 entitled "Analog Voltage to Pulse Rate or Analog to Frequency Converter", M. A. Schaffer issued Dec. 1, 1981. U.S. Pat. No. 4,303,985 describes a circuit arrangement for a voltage to frequency converter having a source of precision voltage which is utilized for the development of the analog-to-frequency conversion. The voltage to frequency converter of U.S. Pat. No. 4,303,985 develops a digital pulse train output signal whose pulse rate is proportional to the amplitude of the input voltage.
Another voltage to frequency converter is described in the specification sheets 5-186 to 5-191, printed in U.S.A. July, 1978 of Burr-Brown Research Corporation of Tuscon, Ariz. for their VFC32 device. The VFC32 device of Burr-Brown develops a digital pulse train output signal in a manner similar to the circuit of U.S. Pat. No. 4,303,985 and whose repetition rate is proportional to the amplitude of an analog input voltage.
In certain types of applications it may be desired for a voltage to frequency converter to develop a digital pulse train output signal whose rate is not restricted to being proportional to the amplitude of the applied analog input voltage. For example, a voltage to frequency converter may be desired to perform an arithmetic operation for squaring an input function in its development of the output pulse train. The squaring function may be desired for certain types of computations requiring numerical analysis. These computations may be related to a typical function such as the square of an analog-type-unwanted current (I.sup.2) flowing within a transmission line so as to determine a power loss quantity such as I.sup.2 R for monitoring purposes such as instrumentation. It is desired that this typical instrumented quantity (I.sup.2 R) be accurately developed by the voltage to frequency converter. The accurate development of this squared type function is somewhat hindered in that for relatively low values of monitored current of a transmission line, abrupt changes may cause the frequency converter to generate an abrupt change in its developed output signal which, in turn, may affect or degrade the accuracy of the voltage to frequency converter.
Accordingly, an object of the present invention is to provide a voltage to frequency converter having an accurate output frequency signal proportional to the square of the applied analog-type signal.
Still further, it is an object of the present invention to provide means for smoothing abrupt jumps in the voltage to frequency converter output signal which otherwise occur at low input signals for small percentage changes in the signal applied to the voltage-to-frequency converter.